Small-sized devices such as portable communications devices are equipped with means for notifying the user, for example, of incoming calls or specified hours. The notifying means most widely used is a bell or like means for producing a sound. However, in view of a nuisance to people in the surroundings, more widely used in recent years are small devices which have incorporated therein not only notifying means resorting to sound but also means for vibrating the device for notification so as to use both the notifying means or selectively use one of them in accordance with the situation. For example, FIG. 10 shows a portable telephone of the prior art. With reference to FIG. 10, the portable telephone has a telephone body 101, antenna 102, speaker 103 for incoming speech, microphone 104 for outgoing speech, display 105 and push buttons 106. The telephone body 101 has a ringer speaker 107 for giving notice of incoming calls with sound, and a vibration motor 108 for giving notice of incoming calls with vibration. With the prior art, it is general practice to incorporate means for notifying with sound and means for notifying with vibration into the device. The need to use the two separate notifying means therefore entails the problem that it is difficult to compact the device.
Accordingly, the present applicant invented a notifying vibration generator having the two functions of notifying with sound and notifying with vibration, and has already filed Japanese Patent Application No. 161399/1996 on this invention. FIGS. 11, (A) and (B) show this notifying vibration generator 109 of the prior application. The vibration generator 109 comprises two vibration systems, and a fixed member for supporting the vibration systems. According to this embodiment, the fixed member 110 comprises a lower case 110a for supporting the first of the vibration systems, and an upper case 110b supporting the second vibration system and joined to the lower case 110a. The lower case 110a and the upper case 110b, when joined, define an interior space for accommodating the two vibration systems. The upper case 110b is centrally formed with an opening 111 for propagating sound waves to the outside therethrough. The first vibration system comprises a first spring body 112 made of an elastic material such as a thin metal plate, rubber or resin and deformable perpendicular to the plane thereof, and a first vibrator 116 comprising a permanent magnet 113. The first vibrator 116 is attached to the first spring body 112 toward the inner periphery thereof as by bonding, and the first spring body 112 is attached at its outer periphery to the lower case 110a as by bonding, whereby the first vibration system is adapted to vibrate upward and downward relative to the lower case 110a. An upper yoke 114 and a lower yoke 115 are arranged respectively on and beneath the permanent magnet 113 providing the first vibrator 116 to prevent the magnetic field from leaking to the outside and to efficiently produce an electromagnetic force by the interaction of current and the magnetic field, whereby a magnetic circuit is formed. The magnet 113 is annular and has an N pole on its upper surface and an S pole on its lower surface. The upper yoke 114 is in the form of a ring having a vertical wall along the inner periphery thereof. The lower yoke 115 is in the form of a disk having a central protrusion. A magnetic gap 121 is formed inside the vertical wall of the upper yoke 114 around the central protrusion of the lower yoke 115 for permitting upward and downward movement of the second vibrator 117 to be described below.
On the other hand, the second vibration system comprises a second spring body 122 made of the same elastic material as the first spring body 112 and deformable perpendicular to the plane thereof, and a second vibrator 117 comprising a coil 118. The second vibrator 117 is positioned radially inwardly of the second spring body 122 and attached thereto as by bonding. The second spring body 122 has its outer periphery attached to the upper case 110b as by bonding, whereby the second vibrator 117 is adapted to vibrate upward and downward relative to the upper case 110b. The second vibrator 117 comprises the coil 118, a bobbin 119 supporting the coil 118, and a diaphragm 120 for producing sound waves. The bobbin 119 is hollow cylindrical and attached to the second spring body 122. The coil 118 is provided around the bobbin 119. The diaphragm 120 is disposed on the upper end of the bobbin 119. The coil 118 and the bobbin 119 are arranged in the magnetic gap 121 of the first vibrator 116 movably. Indicated at 123 are the terminals of the coil 118, and at 124 rubber or like cushions. The lower case 110a and the upper case 110b provided with the respective vibration systems are joined as described above, and the terminals 123 of the coil 118 are electrically connected to a circuit for passing electric current of predetermined frequency through the coil. Formed in the first vibrator 116 at this time is a magnetic circuit including the permanent magnet 113, upper yoke 114, lower yoke 115 and magnetic gap 121. The magnetic field in the gap 121 is directed radially inwardly thereof. Assuming that the current through the coil 118 is counterclockwise when the generator is seen from above, an interaction between the magnetic field and the current intersecting the field produces repulsion between the first vibrator 116 and the second vibrator 117. Conversely, if the direction of current through the coil 118 is reversed, attraction acts between the first vibrator 116 and the second vibrator 117. Accordingly, each of the first and second vibrators 116 and 117 is subjected to a periodic electromagnetic force as an external force by periodically varying the value of current to be passed through the coil 118. Thus, each of the first vibration system and the second vibration system can be caused to generate forced vibration by the combination of the permanent magnet 113 and the coil 118. By virtue the restoring force of the first spring body 112, the first vibration system transmits the forced vibration to the case 110, vibrating the device and realizing notification with the vibration. With the second vibration system, the forced vibration causes the diaphragm 120 of the second vibrator 117 to vibrate the air to produce sound waves, which propagate to the outside through the opening 111 in the upper case 110b. If the sound waves have an audio-frequency (about 20 Hz to about 20 kHz), notification with sound can be realized.
FIG. 12 is a graph showing the amplitude characteristics of the vibrators of the notifying vibration generator relative to the frequency of current passed through the coil 118 thereof. The first vibrator 116 and the second vibrator 117 have respective natural frequencies which are different, and are adapted to be maximum in amplitude respectively at f0 (e.g., 100 Hz) and f1 (e.g., 3 kHz).
The signal to be applied to such a notifying vibration generator of the prior art is in the form of rectangular waves rather than sine waves in view of the efficiency of the vibration relative to the power consumption and the advantage of the circuit construction for preparing the signal. However, if merely applied, rectangular waves encounter the problem that when the first vibrator 116 functions to generate mechanical vibration for notification, the high-frequency component of the rectangular waves applied also produces an unnecessary sound at the same time although no problem arises when the second vibrator 117 is vibrated to produce sound for notification. FIG. 13 is a graph showing the sound pressure level measurements obtained when rectangular waves of 110 Hz are applied to the notifying vibration generator for the generation of mechanical vibration. The graph reveals higher sound pressure levels in the range of about 1.2 kHz to 1.8 kHz, indicating that a disagreeable sound is produced along with mechanical vibration. The generation of such a disagreeable sound is the problem to be overcome since vibrating the device for notification is intended to avoid a nuisance to people in the surroundings as previously mentioned.
With the prior art described, notification with both vibration and sound can be realized by a single notifying device, which can therefore be compacted. When the notifying device of the prior art is further given the function of a speaker for incoming speech, there is the possibility of further compacting the device.
From the above viewpoint, an object of the present invention is to realize a notifying vibration generator which is singly adapted to give notice both with vibration and with sound and is yet capable of generating great vibration efficiently with reduced current consumption, and also to realize a portable communications device having incorporated therein a notifying vibration generator thus adapted and further having the function of a speaker for incoming speech.